Last year's capacity addition is more than all of previous years installations put together. As much as 22 per cent of capacity was added through PPA (power purchase agreements) based projects.

The rooftop solar market growth is directly linked to improving economics of rooftop solar. Most commercial and industrial consumers can reduce their power bills by 20-30 per cent with rooftop solar power.

The growth in rooftop solar installations is expected to continue in the years to come and the market is expected to reach a total capacity of 12.7 GW by 2021.

The report also highlights that commercial and industrial consumers dominate the market with 63 per cent of installed capacity. Grid parity for these consumers has now been achieved in 17 out of the 19 largest states in India.

In states such as Maharashtra and Haryana, tariff differential between grid power and rooftop solar power can be as high as 30 per cent, it said.

This has been much steeper than what most analysts had earlier predicted and has helped in achieving the existing growth rate, the report added.

Tamil Nadu, Maharashtra and Gujarat are leading in terms of total installed capacity. The government rooftop solar segment has grown to over 10 per cent in total installed capacity.